The synthesis of preferred polybenzimidazole based high performance fibers requires the selective condensation polymerization of 2,3,5,6-tetraaminotoluene (“TAT”) with various substituted and unsubstituted aromatic diacids, such as 2,5-dihydroxyterephthalic acid (“DHTA”). A 1:1 complex formed between TAT and the aromatic diacid represents the monomer of choice for the production of a high molecular weight, high strength fiber, with this ratio being of utmost importance. These materials are typically prepared using aqueous conditions. However, when desired aromatic diacids with at most limited solubility in water are utilized, alternate conditions need to be developed. In addition, in identifying such alternate conditions, safety concerns, especially with respect to sensitizing properties of some intermediates, need to be addressed.
There thus remains a need for a safe, efficient process for the production of suitable high-purity TAT-diacid monomer complexes that can be polymerized to a high molecular weight polymer material for producing high-performance fibers.